People who have an exaggerated blood pressure response to low-level exercise may be at increased risk of heart disease, a study suggests.

Researchers found that among more than 3,000 middle-aged adults, those whose diastolic blood pressure rose the most during exercise were at increased risk of developing heart disease over the next 20 years.

Diastolic blood pressure refers to the second number in a blood-pressure reading, while systolic blood pressure refers to the first number.

Past studies have shown that an exaggerated systolic response to exercise may predict heart trouble. But the new findings, published in the American Journal of Cardiology, suggest that the diastolic response is even more important.

The results are based on data from 3,045 men and women who had their blood pressure monitored while they walked on a treadmill. The participants were 43 years old, on average, and none had a history of cardiovascular disease.

Over the next 20 years, 421 men and women suffered a heart attack, stroke or other cardiovascular complication.

The researchers found that those who had shown the largest diastolic responses to exercise were 41 percent more likely to suffer a heart problem or stroke during the study period.

In contrast, the systolic blood pressure response was not an independent predictor of future heart trouble, according the researchers, led by Dr. Gregory D. Lewis of Harvard Medical School in Boston.

“The amount of exercise performed in this study is indicative of levels of daily physical activity, and therefore blood pressure measurements from our study reflect blood pressure to which patients are exposed on a daily basis,” Lewis told Reuters Health.

What’s not clear, according to Lewis, is why some people have a marked blood pressure reaction to such day-to-day activity levels.

He said that more research is needed to answer this question - and to see whether exaggerated blood pressure responses to exercise can be prevented.

SOURCE: American Journal of Cardiology, June 1, 2008.